ZL1 A Chevy Big-Block Legend - ZL1 At A Time

On The Assembly Line With GM's Limited Production, All-Aluminum Ram Jet Big-Block

Exclusive!Just the name "ZL1" conjures thoughts of the ultimate Chevy big-block-a legend in its own time.

As any dedicated Bow-Tie fan knows, the ZL1 engine was a special, all-aluminum version of the Rat motor. That means the block and cylinder heads. In its day, a few were slipped into production vehicles, including 69 '69 COPO Camaros and a pair of super-rare '69 Corvettes.

A couple hundred more of the engines were made available to racers through the early '70s, including John Greenwood, who had considerable success using one of these alloy powerplants in his SCCA national championship-winning Vette.

The ZL1 legend might have remained a tall tale of the Chevy performance mythology, but it was brought into the 21st century when the engine block's original tooling was discovered a few years ago. After a few updates to the initial design, to improve oiling and increase overall strength, GM added an all-new ZL1 assembly to its Performance Parts repertoire.

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And, recognizing the success of previous special-edition crate engines, such as the ZZ-430, GM rightfully decided to offer a unique crate engine based on the alloy Rat-the Ram Jet ZL1. The port-injected combination is rated at 510 horses and 493 ft-lb of torque, and includes the necessary computer to manage the electronically controlled engine.

Other changes were made to the engine, too, to update the ZL1 to modern performance expectations, including a roller camshaft (albeit a solid roller). The Ram Jet induction setup is the same offered on other big-block crate engines.

There's one big difference between the ZL1 of old and its contemporary reincarnation, however: displacement. The '69 ZL1 displaced 427 ci, while the ZL1 crate motor is a 454. Why? Because GM says the longer-stroke 454 produces a broader torque curve, resulting in a better driving engine.

Only 200 of the engines were built, each specially numbered with engraved valve covers and throttle body.

The engines were painstakingly put together on a unique, three-station assembly line in suburban Detroit. GM sub-contracted the assembly duties to Performance Assembly Solutions (PAS), which collected the individual components, assembled the engines, and crated them for delivery.

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Recently we were fortunate enough to get an exclusive peek at the PAS assembly line, and followed the assembly of several of the Ram Jet ZL1 engines. Interestingly, the engines aren't completely finished when the reach the end of the line.

"With the Ram Jet upper intake, the engines are too difficult to install in a vehicle, so the engines are shipped without the intake manifold installed to save the customer time and effort," says PAS's Chris Zucker. "There are actually two crates with the package; one contains the long-block and many accessories, and the second crate contains the upper intake, the starter and other things."

A start-up kit accompanies each engine, and contains detailed instruction for installing the remaining parts, as well as an oil pump primer. There's also a diagnostic code reader that helps diagnose any problems down the road.

"The timing for each ZL1 is roughed in on the assembly line," says Zucker. "But, of course, the owner really has to fine tune it per the provided instructions."

Creation of the engines really starts at Swartz Machine Company, in Warren, Michigan, where the aluminum block castings are machined. They're delivered to PAS in ZL1-labled crates, hoisted on to engine stands, and then the air and torque wrenches really begin to turn.

"The blocks are measured and inspected before any assembly is started," says Zucker.

In the three stages of the engines' journey down the line, the first stage lays the crank, main caps, cam, timing chain and cover. The second stage completes the short-block, while the third stage finishes the long-block and "dresses" the engine, as well as performs details such as lashing the valves.

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